For example, television receivers receive television broadcasting signals, displays images in television broadcasting programs, and outputs sound accompanying the images.
Conventional television receivers are produced so as to operate alone. Therefore, when users buy new television receivers, the users do not need to have the old ones, and discard them in many cases even if they can be used.
If a great number of connected television receivers provide a higher function than one television receiver, television receivers which can be used are prevented from being discarded, thereby contributing to the effective use of resources.
At homes with babies and little-children, or aged persons, for example, it is difficult to always monitor them, and, in general, nursing persons including persons at the homes go and look after the babies and little children or the aged persons regularly or irregularly.
In these cases, however, the nursing persons have significant loads, and therefore, means for reducing the loads of the nursing persons have been demanded.
As such means, for example, monitoring camera systems are used in which babies and little children or aged persons in rooms are image-captured, and the images are displayed at a display unit in another room.
In conventional monitoring camera systems, however, the images sent from cameras need to be checked always, regularly, or irregularly, and the loads imposed on nursing persons are reduced to some extent, but they are still large.
Television receivers are used in many houses. When a monitoring camera system is used, it is necessary to install a display unit for the system in addition to a television receiver used, and thereby reducing the house space.
The images sent from a camera of the monitoring system can be displayed at a television receiver used in the house.
When the images sent from a camera of the monitoring system are displayed at a television receiver used in the house, however, the nursing person cannot view television broadcasting programs at the television receiver.
It is also possible for the nursing person to switch at the television receiver between television broadcasting programs and the images sent from a camera of the monitoring camera system. However, this switching operation is troublesome, and further, a case may arise in which the nursing person forgets to switch and does not notice an emergency state in a worst case.